Process for the preparation of zinc alkyl orthophosphates

ABSTRACT

AN IMPROVED PROCESS FOR THE MANUFACTURE OF ZINC ALKYL ORTHOPHOSPHATES IS DISCLOSED. PHOSPHORUS PENTOXIDE IS REACTED WITH AN ALIPHATIC ALCOHOL CONTAINING FROM ABOUT 10 TO 14 CARBON ATOMS, SUCH AS TRIDECYL ALCOHOL, IN THE PRESENCE OF AN AROMATIC SOLVENT AND THE RESULTING ORTHOPHOSPHATE ESTER IS NEUTRALIZED USING A SOLID ZINC SALT SUCH AS ZINC CARBONATE OR ZINC ACETATE, IN AMOUNTS OF AT LEAST ABOUT 50%, UP TO ABOUT 85%, PREFERABLY 70% TO 80%, OF THE ZINC REQUIRED TO FULLY NEUTRALIZE THE ESTERS. THE ZINC ALKYL ORTHOPHOSPHATES ARE USEFUL AS ADDITIVES IN GASOLINES.

Un.ited States Patent 01 ice 3,655,704 Patented Apr. 11, 1972 ABSTRACT OF THE DISCLOSURE An improved process for the manufacture of zinc alkyl orthophosphates is disclosed. Phosphorus pentoxide is reacted with an aliphatic alcohol containing from about to 14 carbon atoms, such as tridecyl alcohol, in the presence of an aromatic solvent and the resulting orthophosphate ester is neutralized using a solid zinc salt such as zinc carbonate or zinc acetate, in amounts of at least about 50%, up to about 85%, preferably 70% to 80%, of the zinc required to fully neutralize the esters. The zinc alkyl orthophosphates are useful as additives in gasolines.

The present invention relates to an improved process for the manufacture of zinc alkyl orthophosphate ester salts. In particular, the present invention relates to a method for preparing zinc alkyl orthophosphate esters by reacting an aliphatic alcohol of about 10 to 14 carbon atoms with phosphorus pentoxide in an aromatic solvent, thereby forming an alkylphosphate ester, and reacting the resulting orthophosphate ester with a solid zinc salt in amounts of about 85% or less of the moles of zinc needed to neutralize the acid sites of the phosphate ester.

Zinc organo orthophosphates are known surfactants and deposit modifiers when used in fuels for gasoline engines. For example, in US. Pat. 3,481,717, issued Dec. 2, 1969, there is disclosed and claimed an improved gasoline composition which consists essentially of hydrocarbon gasoline, an anti-knock quantity of a tetra-lower-al-kyl-lead compound, a gasoline-soluble zinc organo phosphate salt and gasoline-soluble phosphorus compound. These zinc organo orthophosphate salts when used with other gasoline-soluble organo phosphorus compounds such as cresyl diphenyl phosphate have been found to improve octane requirement increase, rumble and spark plug fouling in engines. As noted in the aforesaid U.S. Pat. 3,481,717, these zinc additives can be incorporated along with other known additives such as tetra-lower alkyl lead compounds.

Typically, the zinc organo phosphates are prepared by reacting an alcohol with phosphorus pentoxide in a solvent forming an organo orthophosphate ester. The alcohol is generally an aliphatic, including cycloaliphatic, alcohol, and preferably can be an alkanol, straight or branchedchain, or an alkyl-substituted phenol whose alkyl substituents contain up to about 18 carbon atoms. These esters are then reacted with a zinc salt to prepare the zinc organo orthophosphate additives. It has been found, however, that the preparation of these additives has been hampered by emulsion formation and product instability during the process of manufacture. The zinc additives prepared were also reactive over water, a condition which precluded their use in gasoline. These compounds decomposed at gasoline-water interfaces in storage tanks forming a precipitate that causes filter plugging.

It has now been found that relatively stable, waterunreactive zinc alkyl orthophosphate additives suitable for use in gasoline can be prepared by reacting phosphorus pentoxide with an alkanol containing from about 10 to 14 carbon atoms, preferably 12 to 13 carbon atoms, in an aromatic solvent to form an alkyl orthophosphate ester and reacting the resulting ester with a reactive, solid zinc salt of an inorganic or an organic acid, preferably a form of zinc carbonate or zinc acetate, the zinc salt being pres ent in an amount sufficient to provide up to about 85% and at least about 50%, preferably about 70 to 80%, of the number of moles of zinc needed to neutralize the acid sites of the phosphate ester.

The reaction of the aliphatic alcohol and phosphorus pentoxide to prepare the partial esters can be conducted at temperatures of about 100 F. to 250 F., preferably about 130 F. to 200 F, for a period of time sutficient to elfect substantially complete reaction, usually about 1 to 15 hours. The reaction is carried out in the presence of an inert, liquid, essentially aromatic hydrocarbon solvent, generally boiling in the gasoline range or higher, e.g., at least 50% or more boiling in the gasoline range, preferably at least about or in an amount sufiicient to dissolve the zinc salt formed by the partial neutralization. Toluene, xylene and mixed hydrocarbon solvents composed predominantly of aromatics are preferred solvents and it has been found that paraffinic solvents may yield unstable products. A suitable molar ratio of alkanol to phosphorus pentoxide can be from about 1 to 6: 1, preferably about 2 to 4:1.

The zinc alkyl orthophosphate ester salt additives are prepared by reacting the resulting ester with a solid zinc salt of an inorganic or organic acid, such as zinc chloride, zinc sulfate, zinc carbonate, basic zinc carbonate (Zn (CO -(-OH) or zinc acetate, with the zinc salt being present in amounts sufiicient to provide at least about 50% and up to about preferably 70 to 80%, of the equivalent number of moles of zinc needed to neutralize the acid sites of the phosphate ester. Zinc acetate and zinc carbonates are preferred as is the essential absence of added water in the neutralization.

The partially-neutralized zinc salts of this invention can be incorporated into a gasoline composition consisting essentially of a hydrocarbon gasoline, and anti-knock quantity of a tetra-lower alkyl-lead compound, such as tetraethyl lead and a gasoline soluble phosphorous compound having the formula:

Ro OR RO o where R is a lower alkyl phenyl radical of 7 to 15 carbon atoms and R is selected from the group consisting of phenyl and R. The zinc salts of this invention can be present in the gasoline compositions in a small but effective amount suflicient to improve octane requirement increase, rumble and spark plug fouling, which amount can be, for example, from about 0.025 to 0.3 milligram atom of metal per gallon of the gasoline. The gasoline soluble phosphorous compound is preferably cresyl diphenyl phosphate and can be present in an amount of from about 0.05 to 0.5 theory, preferably about 0.2 to 0.3 theory, based on the lead content of the gasoline. The term theory as applied to the gasoline soluble organophosphate additive means the amount required to react stoichiometrically with the lead so that all of the lead atoms and all of the phosphorous atoms form Pb, (PO9 The following example demonstrates the process of the present invention.

EXAMPLE Zinc organo orthophosphates were prepared by reacting phosphorus pentoxide with different alcohols and then reacting the resulting product with basic zinc carbonate and zinc acetate in varying equivalent concentrations. Products which were suitably formed by the reaction were subjected to a test to duplicate field storage stability.

Field tank storage stability was simulated by storing a commercial type leaded gasoline with the additive at TABLE ICoutinued 100 F. for 30 days over water bottoms with a pH of 6, f gi Preparation 7 or 8. The ratlo of gasohne to water was 9 to 1' The 2 Pre aration was identical to Run 1 except 257 less equi conditlons and amounts of preparatlon are shown below 5 n va ience basic inc carbonate was usedand tf e rea tion in Table I. Table II shows the effect of concentration of 3 Pwas rigi witlgs 115516352: ag ladldgge t 7 1 SS 1 zinc on the preparation of the additive. Table III shows figgi g g zncoawas used. P a 6 the eifects of the solvent present during the reaction on 4-.. Same bgzicl procedure as Run 1 except cold water washes were e the stability oi the product. Table IY'shows the effect of Same procedure as Run 1 expept 5% excess equivalence the concentration of zinc on the stability of the products. 10 basic zinc carbonate was2gsed. I in Table V shows the effect of diiferent alcohols on product 6 %%.}f g fi ff 5 m 9 Z acetate was used stability and Table VI ShOWS the results of the storage 7 Sane a: Run 1 eicept 30% less equivalence basic zinc car- Stabflity tests on the products formed 8- sai gis l t fii l xcept 20% less equivalence basic zinc car- As may be noted from the tables, zinc carbonate yields bonate gas ulsed. t 1 i 1 b i a slightly more stable product than zinc acetate at 100% 9 gfigg gg gg e55 equ Va as Zinc of equivalent zinc concentration. At 80% of equivalence 10 Same as Run 1 exgeptitg0i7golesls efquizalengel basic zinc (number of moles of Zinc needed to neufralize the i l 11 sa i i e g s ll u n l i gp t 10% ex es s egi ivi l nce asic zinc i cce ta e. car onate was use Sltes of the Qhosphates ester? elther Zmc Sa t S a p 12 Same as Run 1 except toluene was used as the solvent. The Paraffimc solvent used In Runs 19 and i d ii 13 Same as Riin ltexcept the basic zinc carbonate was added e a over 0m nu es. unstable product Whlle h aromatlc Solvent yle 20 14 Same as Run 1 except 30% less equivalence basic zinc carstable Product Although lsodecanol 3:150 2925 1,? l l bonizte was used along with tridecanol instead of iscdecproduct without problems 1n preparation, a e s ows 15 s arm as Run 1 exce t zinc acetat a s d M 2 1 that this additive was more unstable in the storage stagg equivalence? ew e W 0% e53 bility test. Zinc tridecyl orthophosphate showed even bet- 16 Same as Run 1 except less equivalence basic zinc carbonate was used and added b slow addition 0 20 ter storage stability than the base fuel without any zinc minutes y dditi 17 Same as Run 1 except 20% less equivalence basic zinc carlooniate was used and octyl alcohol was substituted for TABLE I so ecano 18 Same as Run 1 except 20% less equivalence basic zinc carbonate was used and hexadecyl alcohol was substituted 331) Preparation 19 saf e fi ii i l except 307 less equivalence b si i 0 a 0 Z no 1 Phosphorus pnentoxide (.3 mega) was re act e d with gt n 1 c'arb on t e vg reacted and water white distillate was isodecanol .9 mole) inaroun bottom as us ng use as e o ven ot140 arom itic solvent. The mixture was stirred at 185 F. 20 Same as Run 1 except 20% less equivalence basic zinc carfor one and one-half hours. The product, isodecyl orthsbonate was added slowly using water white distillate as phosphate was washed three times with hot water (185 the solvent. F.). Basic zinc carbonate (.225 mole, 100% equivalence of the ester acid sites) was added to the ester and stirred 3 5 at 185 F. for one and one-half hours. The product was washed with three hot water washes, and filtered.

TABLE II.EFFECTS OF ZINC SALT ON ZINC ALKYL PHOSPHATE PREPARATION Zinc cone. (percent Zinc salt used equivalent) Preparative problems Product stability Run:

8 Zinc carbonate, basic 80 None Good.

.do 1 Some emulsion, poor filtering-. Clouded 15 Zinc acetate 80 None Good. 6 do 10 Bad emulsion, poor filtering Precipitate.

1 Clear products were rated good.

TABLE III.-EFFECTS 0F SOLVENT ON ZINC ALKYL PHOSPHATE PREPARATION Zinc cono. (oi' equiva lent), Solvent percent Preparative problems Product stability Run:

7 140 Aromatic None Good. 4 do. 100 Bad emulsion, poor filtering.. Precipitate forms. 20 Water white distfi. Some em ion Do. 19 do. 70 None Do. 12 Toluene 1 d0 Do.

1 Clear products were rated good.

2 140 Aromatic is a. high, e.g. about or more, aromatic content hydrocarbon solvent having an API gravity of 29.5, an initial boiling point of about 360 F. and an end boiling point of about 395 F.

3 Water white distillate is a paraifinic-type hydrocarbon solvent.

TABLE IV.-EFFECT OF ZINCPCONCENTRATION ON ZINC PHOSPHATE 1 Clear products were rated good.

TABLE V.-EFFEGT OF DIFFERENT ALCOHOLS ON ZINC ALKYL PHO SPHATE PREPARATION Characteristics 30% less ZnC 03, isodecyl a1cohol Trace. Trace- Trace. less ZnOO isodecyl alcoho1 Fail .do.-. li31o.

9.- 10% less ZllCOa, isodecyl alcohol ..do Fail... Fa 14.- less ZnCO tridecyl alcohol. OK Trace. OK. Base- No additives Trace... do Trace It is claimed:

1. A process for the manufacture of a zinc alkyl orthophosphate which comprises reacting an alkanol containing from about 10 to 14 carbon atoms and phosphorus pentoxide in an aromatic hydrocarbon solvent at a temperature of from about 100 to 250 F. for a time sufiicient to form the corresponding alkyl phosphate ester and reacting the resulting ester with a solid zinc salt in an amount sufficient to provide from about to 85% of the moles of zinc needed to fully neutralize the acid sites of the phosphate ester.

2. The process of claim 1 wherein the zinc salt is present in an amount of from about to of the moles of zinc needed to fully neutralize the acid sites of the phosphate ester.

3. The process of claim 2 wherein the zinc salt is zinc acetate or zinc carbonate.

4. The process of claim 3 wherein the process is carried out at a temperature of from about to 200 F.

5. The process of claim 1 wherein the molar ratio of alkanol to phosphorous pentoxide is from about 1 t0 6: 1.

6. The process of claim 5 wherein the molar ratio of alkanol to phosphorus pentoxide is from about 2 to 4:1.

7. The process of claim 5 wherein the alkanol contains 12 to 13 carbon atoms.

8. The process of claim 7 wherein the alkanol is tridecyl alcohol.

9. The process of claim 6 wherein the alkanol contains 12 to 13 carbon atoms.

10. The process of claim 7 wherein the alkanol is tridecyl alcohol.

References Cited UNITED STATES PATENTS 3,401,184 9/1968 Revukas 260429.9 X 2,790,766 4/ 1957 Otto 260429.9 X 2,193,965 3/1940 Hochwalt 260980 X 2,676,975 4/1954 Fortess et a1. 26098-0 2,586,897 2/1952 Woodstock 260980 X TOBIAS E. L-EVOW, Primary Examiner H. M. S. SNEED, Assistant Examiner U.S. Cl. X.R. 

